Filter devices of this type are readily available on the market in a plurality of constructions and versions. Such filter devices are used mainly to filter fouling in fluids such as hydraulic oil. Fouling of the hydraulic oil occurs in the installation or in the start-up of the respective hydraulic system. In addition to this initial fouling, fouling can occur during operation, for example, by penetration of dirt at the hydraulic tank as a result of inadequate tank ventilation, pipe penetrations, piston rod seals, and the like. Fouling can occur within the fluid stored in the hydraulic tank, especially in the hydraulic systems of heavy machinery such as earth moving machines, excavators, or the like. Furthermore, in these types of applications of the filter device, effecting filtration directly in the region of the hydraulic tank, for example, by installing the filter device directly in the tank, can be useful.
Under conditions of use as prevail in operation of the filter device in construction machinery or other machinery operated in the open, due to the higher fouling rates that arise, frequent changing of the filter element must be done. In the course of handling the used, i.e., fouled, filter elements, in these known solutions, the risk exists that contamination both of the system, i.e., especially of the filter housing and the tank, and also of the environment will occur.
DE 10 2006 011 844 B4 discloses a filter element with a filter bowl that borders an interior, with a bottom part having a flow passage, with a filter medium located in the interior of the filter bowl, and with a valve body of a valve apparatus. The valve body can be actuated by the fluid pressure on the fluid passage of the bottom part. The valve body has a screen-like, flexible closing jacket that blocks the fluid passage in the opened-up state, is moved by the fluid pressure in the direction to its closed position, and clears the fluid passage. The closing jacket in its central region is fixed on a carrier within the filter element. The ring body of the bottom part makes a ring edge forming the valve seat sealing surface and projecting to the inside.
DE 10 2005 001 828 A1 discloses a generic filter device, especially a fitting for forming a fluid-carrying connection to a plastic container, preferably in the form of a tank for accommodating a fluid, specifically a hydraulic fluid. The fitting has a connection part in the form of a hollow body with a jacket extending along one longitudinal axis of the hollow body between its ends. The hollow body is embedded in the plastic of the wall of the container such that one open end of the hollow body on the edge of an opening of the container and at least one partial region of the jacket of the hollow body are surrounded by the plastic of the wall of the container.
The hollow body is preferably produced from a metallic material, enables not only the reliable connection to connection parts or attachment parts forming a component of the pertinent hydraulic system, but also contributes concomitantly to reinforcing that region of the plastic container or tank located in the region of the opening.
With regard to the possibilities of comparatively simple forming, of low weight and of corrosion resistance relating to the plastic tank, the known solution, however, leaves much to be desired. The known solution is also relatively complex with respect to the host of components to be used and is therefore costly in production.